Pneumatic vibration-inducing device

ABSTRACT

There is provided an improved piston structure enabling the attainment of higher frequencies of vibration without sacrifice of piston diameter characterized by a cylindrical piston having a density which is less than the density of the housing. In a specific embodiment, the piston is hollow.

United States Patent [72] Inventor Warren C. Burgess, Jr.

Avon Lake, Ohio [21 1 Appl. No. 816,497 [22] Filed Apr. 16, 1969 [45] Patented Aug. 24, 1971 [73] Assignee Burgess & Asocintes, lnc.

Lakewood, Ohio [54] PNEUMATIC VIBRATION-INDUCING DEVICE 5 Claims, 2 Drawing Figs.

[52] U.S.C1 91/234 [51] Int. Cl F01121/02 [50] Field of Search 91/232, 7 234, 392, 227 173/135 [56] References Cited UNITED STATES PATENTS 1,175,621 3/1916 Ekberg 173/135 2,797,664 7/1957 Swanson 91/392 2,861,548 11/1958 Burgess, Jr. et a1. 91/227 355,037 12/1886 Terry 91/234 385,113 6/1888 Grabneret al.... 91/234 1,007,521 10/1911 Boys et a1. 91/234 FOREIGN PATENTS 21,425 1903 Great Britain Primary Examiner-Paul E. Maslousky Attorney-McNenny, Farrington, Pearne and Gordon ABSTRACT: There is provided an improved piston structure enabling the attainment of higher frequencies of vibration without sacrifice of piston diameter characterized by a cylindrical piston having a density which is less than the density of the housing. In a specific embodiment, the piston is hollow.

Patented Aug. 24, 1971 INVENTOR WARREN C. BURGESS, JR.

BY M/Ve/my, Fdrr/ny/on, Paar/re 5 Gordan ATTORNEYS BACKGROUND OF INVENTION AND PRIOR ART This invention relates as indicatedto an improved pneumatic free-piston vibration-inducing device. Reference may be had to U.S. Pat. No. 2,861,548 for disclosure of pneumatic free-piston vibration-inducing devices wherein the piston is a solid member. The principles of operation of vibrators described therein are applicable to the vibrators of the present invention. i

The basic problem which is solved by the present invention is in achieving a high frequency for vibratory conveyors, especially vibratory parts feeders, elg'. bowl-type parts feeders. In the past, such vibratory conveyors have been supplied with free-piston vibrators of the type shown in the aforesaid U.S. patent. The frequency of vibration of a free-piston vibrator at a given pressure increases with a decrease in piston diameter for a given piston length. In certain applications, larger diameter pistons are required in order to generate the momentum and energy necessary to drive the larger vibratory conveying devices, e.g. bowl feeders. The driving action of a track segment in a bowl feeder, for example, on parts being conveyed along such track segment depends upon the frequency with which the segment vibrates and upon the amplitude of vibration or movement of such section. v

The maximum amplitude which can be used to advantage with any given part or material is usually fixed. Above this amplitude, controlled movement of i the part is difficult. The speed of movement of parts along the track is proportional to both amplitude and frequency of vibration. Consequently, in using large piston vibrators to drive large parts feeding bowls (e.g. 36 inches in diameter), an increase in speed of the parts along the trackway was obtainable only by increasing the amplitude at the relatively moderate frequencies of the large vibrators. Thus, limitations upon the speed with which a part could be handled were often imposed. These limitations were exceeded by the demands for the parts being conveyed. In order to increase the speed with which a part could be handled, it was found necessary to develop higher frequencies of vibration.

One method of increasing the frequency is to reduce the length of the piston. The increases in frequency by this method are limited, and there is also a limitation upon how much decrease in piston length can be undertaken. These limitations arise when the ratio of the diameter to the length of the piston exceeds a certain value and the configuration is no longer stable in operation, i.e. the cylinder does not have enough surface parallel to the axisof the piston to guide it in a controlled manner.

It has been found that the parameter used in determining the design of the piston in order to achieve a predetermined frequency depends upon the mass of the piston per unit of area of the piston end exposed to the gases which accelerate and decelerate the piston as it oscillates within the cylinder. In order to achieve high-frequency operation, and also to provide a configuration which is stable in operational respect to the length/diameter ratio, it has been found necessary to effect an apparent density of the piston which is less than that of a conventional solid piston.

BRIEF STATEMENT OF THE INVENTION Briefly stated, the present invention is in the provision of a pneumatic, free-piston vibration-inducing device including in combination a housing, including a cylindrical bore which is closed at each end. Gas inlet means are provided which include a centrally disposed inlet port extending through the housing. Gas exhausting means are also provided which include axially spaced exhaust ports extending through the housing and adjacent each end of the cylindrical bore. A cylindrical piston is provided having an apparent density which is less than the density of the housing, which piston hasan axial length greater than theaxial distance between the exhaust ports so that the piston covers both exhaust ports on dead center, said piston being characterized by an annular shell and means for closing each end thereof. Gas transfer means are disposed in the piston and alternately coact between the gas inlet means and the ends of the cylindrical bore, respectively,

whereby the piston reciprocates in the bore to admit gas under pressure alternately to each end of the cylindrical bore.

The mode of utilizing these vibratory devices is well known and need not be further described'here. Reference may be had, for example, to U.S. Pat. No. 3,023,738 for a description of a system in which the improved vibration-inducing devices of the present invention may be utilized, and to U.S. Pat. No. 3,367,480 for a means for mounting the vibration-inducing devices hereof upon a bowl-type feeder.

BRIEF DESCRIPTION OF THE DRAWINGS v In the annexed drawings:

FIG. 1 is an end view of a vibration-inducing device in accordance with the present invention utilizing a hollow free piston.

FIG. 2 is a cross-sectional view of the device shown in Fig. l as it appears in the plane indicated by the line 2--2 of Fig. 1.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now more particularly to Figs. 1 and 2, there is provided a housing 10 formed of a suitable material such as cast iron or from steel, and including a cylindrical bore 12. To admit a compressed gas, e.g. compressed air, under pressure to the system, there is provided a gas inlet 14 which is centrally disposed in the housing 10. The gas inlet port 14 communicates with an annular groove 16 for distribution of the compressed gas to the piston as hereinafter described. To provide for exhausting of the gas, there are provided exhaust means which include the exhaust ports 18 and 20 adjacent the ends of the cylinder and which are desirably equidistant from the midpoint of the cylindrical bore 12.

As indicated above, the cylinder 12 is closed at each end. To the achievement of such closure there are provided a righthand end closure 22 and a left-hand end closure 23. These may be the same or different and include, for example, means for attachment to mounting means such as shown for example in the aforesaid U.S. Pat. No. 3,367,480, such mounting means not being shown herein but well within the skill of those skilled in the art to provide. In the embodiment shown in the annexed drawings, the end closure 22 includes a flange portion 24 and a plug portion 26. The end closure 23, in like manner, includes a flange portion 25 and a plug portion 27. Flange portions 24 and 25 are suitably drilled to accept means for fastening the end closures to the housing 10. Bolts are shown for such purpose. The end closures 22 and 23 desirably form a very tight closure with the housing 10, and any suitable structure for sealing the ends may be employed. The tighter the closure of the ends of the cylinder 12, the more efficient the operation of the device.

As best shown in Fig. 2, there is also provided a free piston 30 dimensioned for sliding clearance with the cylindrical wall 12. In the embodiment shown, the piston 30 is composed of an annular shell 32 which may be formed of the same material as the housing 10 and the end plates 22 and 23, for example steel. To complete the cylindrical configuration of the piston 30 there are provided end plates 34 and 36 which are conveniently welded to the annular shell 32 as by weldments 38 and 40.

In the embodiment shown in Fig. 2, the annular shell 32 is provided with gas transfer means which alternately coact between the gas inlet means including the inlet port 14 and the annular groove 16 and the ends of the cylindrical bore to the right 'and to the left of the piston 30 as shown in Fig. 2. These means for transmitting gas under pressure to the right-hand end of the cylinder as shown in Fig. 2 include a radial bore 44 communicating with an axial passageway 50 which has an opening 52 in the right-hand end of the piston 30. In like manner, the gas transfer means for feeding the left-hand end of the cylinder 12 to the left of piston 30 as shown in Fig. 2 include a radial bore 42 communicating with an axially extending gas passageway 46 having an opening 48 in the left-hand end of the piston 30. It will be observed that the length of the gas passageways 50 and 46 exceeds one-half of the axial length of thepiston 30 in the embodiment shown.

The mode of operation of the piston 30 in the device shown in Fig. 2 is the same as that described for the solid piston shown and described in US. Pat. No. 2,861,548.

With the embodiment shown in the annexed drawings, it will be seen that the apparent density, i.e. the total weight of piston 30 divided by its total volume is less than the actual density of the material used in the housing. As indicated above, it is conventional to fabricate the housing 10 and the end plates 22 and 23 of a material such as steel. The annular shell 32 and the end plates 34 and 36 are also fabricated of the same material. However, because of the hollow interior of the piston 30, the apparent density of the piston 30 is very much less than the actual density of the material from which the housing 10 and the end plates 22 and 23 are formed. The effect of the radial bores 42 and 44 and the axial passageways 50 and 46 upon the apparent density of the piston is negligible and may be ignored.

In a specific embodiment, the piston 30 may be chromeplated to apply 5/10000 coating. The housing in a specific embodiment is 3.25 in. long exclusive of the end plates. The centerline of gas inlet port 14 is 1.625 in. from either end of housing 10, i.e. at the midpoint of housing 10. Exhaust ports 18 and 20 are spaced equally from the midpoint of housing 10 a distance of 0.917 in. The internal diameter of the cylindrical bore 12 in the specific embodiment is 2.9795 in. finished by honing. The CD. of the piston is 2.9781 including a bulldup for chrome-plating. The piston is 2.000 in. long, and the centerline of radial ports 42 and 44 is 1.250 in. from the remote end of the piston, respectively. The annular groove 16 is 0.25 in. wide and 0.25 in. deep.

For comparative purposes, in devices made of essentially the same steel materials, the maximum frequency of vibration of a solid piston 2 in. in diameter weighing 4.0 lbs. is 1,860 cycles per minute. For a hollow piston 2 in. in diameter weighing 2.4 lbs. of the same length operated at the same line pressure (60 p.s.i.g.), the maximum frequency of vibration is 3,220 cycles per minute.

In the preferred embodiment, the materials of construction of the housing and the free piston arethe same, and most usually of steel. It is contemplated that the piston may be formed of less dense material or materials than the housing. For example, the piston may be composed of a composite including a thin steel outer shell surrounding an aluminum plug, said composite being drilled for gas transfer means substantially as shown in Fig. 2. End plates 34 and 36 may be supplied, or they may be omitted as desired. The cavity defined by the annular shell 32 with or without the end plates 34 and 36 may be filled with a solid material such that the apparent density of the entire body of piston 30 is less than the density of the housing materials. For example, the cavity defined by the annular shell 32 and end plates 34 and 36 may be filled with an epoxy resin. Alternatively, the cavity defined by annular shell 32 may be filled entirely with epoxy resin and end plates 34 and 36 omitted. Where the filler for the internal cavity is a curable liquid material, the axial gas passageways 50 and 46 may be formed by embedding removable plugs, e.g. metal plugs, in the plastic material and after the plastichas solidified under suitable curing conditions, the plugs may be removed to form axial gas passageways 46 and 50 and radial ports 42 and 44 drilled for intersection therewith.

What I claim is: 1. A pneumatic, free-plston vibration-inducing device comprising in combination:

a. a housing including a cylindrical bore closed at each end;

b. gas inlet means including a centrally disposed inlet port extending through said housing;

c. gas exhaust means including axially spaced exhaust ports extending through said housing and adjacent each end of said cylindrical bore;

d. a free cylindrical piston wholly contained within said housing and having an apparent density less than the density of the housing and reciprocable in said cylindrical bore, said piston having an axial length greater than the axial distance between said exhaust ports, and said piston including an annular shell and means for closing each end thereof; and

e. gas transfer means disposed safely in the annular shell of said piston and alternately coacting between said gas inlet means and the ends of said cylindrical bore, respectively, whereby said piston reciprocates in said bore to admit gas under pressure alternately to each end of said cylindrical bore.

2. A vibration-inducing device in accordance with claim 1 wherein the means for closing each end of said piston includes end plates secured to each end of said annular shell to define an internal cavity.

3. A vibration inducing device in accordance with claim 2 wherein the internal cavity is hollow.

4. A vibration-inducing device in accordance with claim 1 wherein the gas transfer means includes:

1. a first gas entrance port positioned in the cylindrical sidewall of said piston to the right of the midpoint of said piston and communicating with an enclosed gas passageway opening through the left end of the said piston, and

2. a second gas entrance port isolated from the first and positioned in the cylindrical sidewall of the said piston to the left of the midpoint of said piston and communicating with an enclosed gas passageway opening through the right end of said piston;

said first and second gas entrance ports being located for alternate gas communicating registry with said centrally disposed inlet port during reciprocatory movement of said piston.

5. A vibration-inducing device in accordance with claim 1 wherein the gas inlet means includes an annular recess in the sidewall of said cylindrical bore communicating with said centrally disposed inlet port.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent. No. 5,601,010 Dated August 24, 1971 lnventofls) WARREN c. BURGESS, JR.

It is certified that error appears in the aboveand that said Letters Patent are hereby corrected as identified patent shown below:

" '6 -.@mn Line 29, "safely" should read solely Signed and sealed this 25th day of January 1972.

a .L J ys E0 M.FLET0HEB, JR. ROBERT G ALK Attesting Officer Commlssloner f Patents 

1. A pneumatic, free-piston vibration-inducing device comprising in combination: a. a housing including a cylindrical bore closed at each end; b. gas inlet means including a centrally disposed inlet port extending through said housing; c. gas exhaust means including axially spaced exhaust ports extending through said housing and adjacent each end of said cylindrical bore; d. a free cylindrical piston wholly contained within said housing and having an apparent density less than the density of the housing and reciprocable in said cylindrical bore, said piston having an axial length greater than the axial distance between said exhaust ports, and said piston including an annular shell and means for closing each end thereof; and e. gas transfer means disposed safely in the annular shell of said piston and alternately coacting between said gas inlet means and the ends of said cylindrical bore, respectively, whereby said piston reciprocates in said bore to admit gas under pressure alternately to each end of said cylindrical bore.
 2. a second gas entrance port isolated from the first and positioned in the cylindrical sidewall of the said piston to the left of the midpoint of said piston and communicating with an enclosed gas passageway opening through the right end of said piston; said first and second gas entrance ports being located for alternate gas communicating registry with said centrally disposed inlet port during reciprocatory movement of said piston.
 2. A vibration-inducing device in accordance with claim 1 wherein the means for closing each end of said piston includes end plates secured to each end of said annular shell to define an internal cavity.
 3. A vibration inducing device in accordance with claim 2 wherein the internal cavity is hollow.
 4. A vibration-inducing device in accordance with claim 1 wherein the gas transfer means includes:
 5. A vibration-inducing device in accordance with claim 1 wherein the gas inlet means includes an annular recess in the sidewall of said cylindrical bore communicating with said centrally disposed inlet port. 